Underpinnings of fire management for biodiversity conservation in ...

Underpinnings of fire management for biodiversity conservation in reserves
• Comparisons between fire seasons – The effect of a prescribed burning program on the area burnt
by unplanned fires (Lang and Gill 1997). In this case, caveats are usually necessary because of the
changing nature of suppression capacity over time, systematic changes in proportions burnt by
prescription, time lags in the system and other factors (Lang and Gill 1997). The results of Lang
and Gill (1997) suggested that there may be a threshold level (10% per year) in which prescribed
burning is most effective in reducing the extent of unplanned fire in south-western WA. The results
of the extreme fires of January–February 2003 in south-eastern Australia show that the extent
of prescribed burning in north-eastern Victoria (say 1 or 2% of the area per year) had little effect
under such circumstances. Unless fuel-modification measures can restrict fire growth early, and
unless sufficient suppression capacity is available and on-the-spot soon after ignition, large fires can
result under conditions of pervasive drought, high FFDI and multiple ignitions.
• Comparisons between regions – The south-western forests of Australia are often regarded as
exemplary in terms of their fire management, and south-eastern Australia compared unfavourably.
More prescribed burning is practised in south-western forests, but there has been no formal
comparison between regions as yet (Esplin et al. 2003, p. 113). It should be noted that the extent
of prescribed burning has been systematically changing in the south-west for decades (Gill and
Moore 1997).
Various performance measures for agencies, based on fire statistics, have been suggested (Esplin et al.
2003, chapter 11).
The results of these studies suggest that the effects of fuel modification vary according to the ignition,
weather, fuel and suppression circumstances, but that prescribed burning generally increases the
chances of successful suppression and decreases the amount burnt by unplanned fires. Adding to the
extent of prescribed fire could alter the total amount burnt in various ways (Bradstock et al. 1995),
including increasing it (King et al. 2006), thereby altering the mean fire interval.
Effects of fires on the environment
The importance of prescribed fires for fire suppression and control has already been outlined. In
reserves for nature conservation, such matters are important but attain added significance in view of
their potential effects on the environment generally, and in particular the organisms that are part of
it. As far as the environment is concerned, it does not matter by who or what a fire is lit; it does not
matter whether it is prescribed, started by an arsonist or the result of a lightning strike. Rather, the
immediate effects of a fire depend on the fire’s properties (e.g. intensity, flame duration and flame
height) and the state of the system at the time (and often soon after). Longer term effects are likely to
depend on the history of fire events – the fire regime. Here, an introduction is given to the effects of
fires and fire regimes on the environment.
Environment is a broad term. In this context it consists of:
• Biodiversity – the variety of life – technically, the diversity of organisms, genes and communities in
natural locations
• Land – including soils, sedimentary deposits, rock types and terrain
• Air – chemical composition and physical characteristics
• Water – for humans as well as animals.
While each of these elements is important, the complexity of the biodiversity issue – the focus of this
publication – needs to be emphasised. In Australia, there are over 20 000 species of native vascular
plants (Orchard 2000), and a large and growing number of naturalised species (Groves et al. 2003).
There are about 2000 species of terrestrial vertebrate animals (Ross 2000) and 200–300 000 species
of invertebrates (Wells and Beesley 2000). These species, let alone others like the estimated 3000
species of lichens, 1500 bryophytes (McCarthy 2000) and 250 000 species of fungi (Grgurinovic
2000), interact with each other and their respective physical environments to various extents. Large
numbers of nameless microbes exist too.
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